Field of The Invention
The invention herein relates to joint systems for concrete structures. More particularly, it relates to a highly fire resistive joint system for use with walls, floors, ceilings and the like, building structures made of a plurality of adjacent concrete panels.
Many buildings are constructed with precast concrete panels comprising the exterior walls, interior walls, ceilings, floors and/or similar portions of the building structure. Such precast panels, which may also be prestressed, are aligned in a generally abutting relationship and form the vast majority of the wall, ceiling, etc. (For purposes of brievity herein the invention will be illustrated in conjunction with a wall. However, it will be understood that the principles of the invention apply equally to floors, ceilings and like structures.) It is conventional in this type of construction to leave a small gap between the adjacent panels to allow for the normal expansion and contraction of the panels. It is therefore necessary to provide some sort of sealing system to close the gaps (or "joints") between the adjacent panels.
Some joint systems for use in interior locations may be essentially for decorative purposes, while others in interior locations may be to provide privacy separation between adjacent rooms. On exterior walls the joint systems will be primarily for weather-sealing. Similar sealing systems on concrete panels which comprise the lower portion of roof decks will also have a weather-sealing function as well as providing a portion of the base for later overlays of tar and other roofing materials.
All of these various joint systems, whether decorative or functional, suffer a serious deficiency which has long been of concern to the construction industry. This deficiency is their very low resistance to fire. While the concrete panel portions of the walls will resist transmission of flame, heat and fire for one or more hours, the joint systems generally fail in a matter of a few minutes. Consequently, fire starting in one portion of a building can be rapidly transmitted throughout the entire building despite the fire resistance of the concrete panels. This of course presents a very serious public safety hazard, particularly in high-rise buildings where fire may spread not only horizontally throughout a single floor, but also vertically to floors above and below through joints in the ceilings and floors. Construction industry people and public safety officials have therefore long sought to devise effective "fire-resistive" joint systems which would provide functional fire resistance essentially equivalent to that of the concrete panels.
For the purpose of description in this specification, the following terminology will be used.
"side of the joint" -- those portions coplanar with the major surfaces of the panels PA1 "depth of the joint" -- the dimension equivalent to the thickness of the panels PA1 "length of the joint" -- the dimension equivalent to the abutting length dimension of the panels PA1 "one-stage joint" -- a joint comprising a straight linear passage (see FIGS. 2 and 3) PA1 "two-stage joint" -- a joint having two straight passages with an offset portion or enlarged portion between them (see FIGS. 4 and 5) PA1 "fire-resistance" -- the ability of a joint to remain operational for at least one hour in the ASTM E-119 fire test